More than 3,800 patients and 200 caregivers have signed up for the Pennsylvania medical marijuana program since Nov. 1, when the registry was launched.

The response “has been extremely positive,” said Rachel Levine, acting secretary of the Pennsylvania Department of Health. At one point last week, the state was registering three patients a minute. It may be weeks, though, before those patients are issued state ID cards that will allow them to purchase medical cannabis products. And those products won’t be available until early 2018.

Last week, the state published a list of about 200 doctors approved to participate in the program. About 50 practice are in Philadelphia and its suburbs. The physician registry will be expanded next week to include doctors granted authority to write recommendations for cannabis products.

A few hundred physicians are unlikely to be enough to support a functional program, some say. In a state of 12.8 million people, patients may struggle to find a participating practitioner. According to the Health Department, about one million Pennsylvanians may qualify for medical cannabis.

Mike Whiter, a U.S. Marine veteran and video producer for NowThis, said he had no problem signing up as a patient. Whiter, who suffers from PTSD, said getting an appointment to see a doctor “has been a bit of a hassle.” His own general practitioner works for the Veterans Administration and is prohibited by federal law from writing a recommendation. “If she could, she would,” Whiter said.

Already, doctors on the state registry have been flooded with calls. An Altoona gynecologist told a local newspaper she had been inundated with requests from men, some of whom were expecting her to write them prescriptions for smokable joints.

Patients with 17 qualifying conditions, from chronic pain to terminal cancer, will be eligible to purchase products at state-approved medical marijuana dispensaries. Those products include vape cartridges, oils, tinctures and lotions, but no smokable forms of marijuana can be lawfully sold in the state.

In addition, doctors can only write recommendations. Official prescriptions, written on a prescription pad, aren’t possible. That’s because all forms of marijuana — including cannabis-derived CBD, a non-psychoactive substance believed to be effective in treating seizures and anxiety — are considered Schedule 1 substances by the Drug Enforcement Administration and, therefore, are prohibited by the federal government.

Broad physician participation is important, said Charles Pollack, director of the Lambert Center for the Study of Medicinal Cannabis and Hemp at Thomas Jefferson University, “and it’s important that we have a lot of patients enrolled at the beginning so we can get off to a good start.”

Other medical marijuana programs in the northeastern U.S. have been hobbled by low numbers of participating doctors. Without physician recommendations, patients are not able to obtain state cannabis cards. Without cards, they can’t get access to medical marijuana.

“The state needs to make sure they’re marketing the program as well as they can,” Pollack said. At present, Pennsylvania does not have a marketing budget to promote the program.

In the Philadelphia region, several state-registered doctors are accepting new patients. Jay Mergaman said his offices had been “swamped” with about 50 calls.

“There’s an opioid epidemic going on out there,” said Mergaman, an anesthesiologist and pain-management specialist who practices in Lansdale and Huntington Valley. “I’m hoping medical marijuana will help my patients wean more quickly off those drugs.”

Charlie Seltzer, a weight-loss and fitness specialist in Center City, said he had fielded calls from dozens of prospective clients but is already booked until December. He said that he would accept only patients with legitimate pre-diagnoses from other doctors and has turned several down as “inappropriate.”

“They wanted it for anxiety or depression,” Selzer said. “I think medical marijuana could be a great option, but in Pennsylvania it’s not legal to write recommendations for those conditions.”